The mechanism of cell surface recognition, adhesion, and deadhesion will be studied in the biflagellated alga Chlamydomonas reinhardtii. During the mating reaction, gametes of opposite mating types adhere to each other via their flagella and ultimately fuse to form zygotes. This adhesive interaction is accompanied by a simultaneous de-adhesion event which, in the presence of protein synthesis inhibitors or an inhibitor of protein glycosylation, leads to loss of adhesiveness of the interacting flagella and disaggregation of the gametes. The long-term goal is to understand the molecular mechanisms of adhesion and deadhesion. The research described in the present application is intended to accomplish the following: 1) the identification, purification, and biochemical characterization of the antigen to which a recently prepared adhesion blocking monoclonal antibody is directed; 2) the characterization of the cellular location and behavior of the antigen before, during, and after mating; 3) the identification and purification, using standard biochemical methods, of flagellar adhesion molecules and comparison of these molecules to the antigen described in 1 and 2; 4) initiation of studies on the molecular biology of adhesion with the immediate objective of learning the methods and vocabulary of this approach and the longer-term objective of cloning genes for adhesion molecules.